Ear infections are among the most common reasons for sick child visits to medical providers. Risk factors for otitis media have been identified in prior clinical studies, but epidemiologic studies of sufficient size to allow generalization to the wider community or national population have been less common. Our goal has been to extend this research by analyzing several U.S. national data sets, collected under the auspices of the National Center for Health Statistics, with support from NIH, and other available population-based datasets. Two papers will soon be published, one on the prevalence and risk factors for placement of tympanostomy ear tubes in US children, and the other a more detailed investigation of the risks for otitis media among children in daycare. We have examined recent trends in physician office, emergency room, and hospital visits for otitis media and treatments in the US and, also, analyzed data from the Third National Health and Nutrition Examination Survey (NHANES III). Findings of these and other studies were presented at the Seventh International Symposium on Recent Advances in Otitis Media (OM) in Ft. Lauderdale, FL, in June 1999. One of these presentations concerned risk factors for children under the age of 6 years. Based on parental reports, in this nationally representative sample, one-third had no ear infections (EI). Of the remainder, 39% experienced their first EI by 6 months of age and an additional 34% in the next 6 months. The children with EI in the first year of life were more likely to have repeated episodes (p<0.001). The results of multiple logistic regression analysis showed that male sex (odds ratio [OR] =1.7; 95% confidence interval [CI] = 1.2- 2.4), any daycare with 6 or more children (OR = 2.8; CI = 2.1- 3.6), black race (OR = 0.4; CI = 0.3-0.7), low household income (OR = 0.6; CI = 0.4-0.9), and a ponderal index at or below the 10th percentile (OR = 2.3; CI = 1.3-3.8) were all associated with frequent EI. Neither breastfeeding nor smoking during pregnancy was associated with frequent EI in the multivariate logistic regression analysis. Both in NHANES III and other studies (the Children in Focus sample of the Avon Longitudinal Study of Pregnancy and Childhood [ALSPAC]) we have studied the prevalence of otitis media with effusion (OME) based on published criteria for flat tympanograms. We have correlated results of hearing exams and other developmental outcomes for children with OME and presented this information at the OM meetings in FL as well. In addition, we have examined outcomes at age 5 for children with otitis media from a longitudinal study, the candinavian Successive Small-for-Gestational Age Birth Study. This study provides further support for poorer developmental outcomes of children with frequent ear infections early in childhood and for those with fluctuating hearing loss associated with OME. This study, based on middle income families in Norway and Sweden with universal access to health care, suggests that even among these relatively advantaged children important differences in developmental outcomes are found, especially for children with fluctuating hearing loss in early childhood. - frequent ear infections, otitis media, ear tubes, prevalence, risk factors, child care, tympanograms - Human Subjects & Human Subjects: Interview, Questionaires, or Surveys Only